Ethics is the logic of proper action. Morality is the logic of proper motivation. Lets say there’s someone who does something that really angers you. You tell yourself that if your government wouldn’t imprison you for killing the offender, you would kill him. In such an instance, in refraining from murdering the offender, it can be said you acted ethically, but not morally. Now lets say you’re told have to do X, Y, and Z or else you’ll be punished postmortem in hell by God. Is it possible for you to behave morally in light of this revelation?
I think without hesitation most evangelicals would say “Yes.” But is it really possible? How can you know for sure that you would, for example, give alms to the poor if you weren’t worried about going to hell for not doing it? Say you tell yourself that you have two motivations for giving alms to the poor: (a) you want to escape suffering in the afterlife, and (b) you want the poor experience happiness. A is a selfish motivation, b is a selfless motivation. If you’re motivated by both a and b, you’re performing an act that is simultaneously selfish and selfless. Is that possible?